However, I'd like to start a thread about free online services that evaluate URLs to determine if they're serving malware of some kind. Recently I saw a short video, which I wish I could find again, that demonstrated the use of this kind of tool - paste in a URL and you get a short report on what, if any, kind of malware is being served there.

Can anyone point out any of these services? Something like http://web-sniffer.net/ that allows a user to view headers, etc.